A vehicle control device includes an operation device for executing a control program which implements an operation to control a vehicle (for example, microcomputer) and a storage device such as a flash read only memory (ROM) for storing the control program. The control program is rewritten into an updated version, for example, by connecting a reprogramming device to the vehicle during a maintenance work and transmitting the updated version of the control program from the reprogramming device to the vehicle control device via an in-vehicle network.
In recent years, a program size of the control program has been increased as processing has become more complicated. Therefore, the processing for rewriting the control program takes a certain period of time in general. PTL 1 discloses a technique for rewriting control software of an automobile control unit in a short time.